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    SubjectRe: undo an mke2fs !!
    On Thursday 06 November 2003 14:34, Theodore Ts'o wrote:
    > On Wed, Nov 05, 2003 at 09:56:01PM -0800, Robert Gyazig wrote:
    > > Hi Ted and others,
    > >
    > > I created a new partition on my disk, and without
    > > noticing the change in the hdaX of the partition i did
    > > an mke2fs /dev/hdaX. :(
    > >
    > > Unfortunately it was my /home partition and was an
    > > ext3 partition earlier. Can anyone please advice on
    > > how to retrieve the old data.
    > >
    > > I read that mke2fs nukes all the meta information, so
    > > does that mean all inodes are destroyed and there is
    > > no hope for me ?!?!?
    > Unfortunately, you're correct. The location of which blocks were
    > associated with which inodes are irretrievably lost.
    > If you had backed up the metadata using an e2image command, you would
    > have been fine, but that command takes a while to run, so most people
    > don't bother to do this. (Not a bad idea for the absolute paranoids
    > in the house would be to run e2image out of a cron script and save the
    > image file on some *other* filesystem.)
    > I've thought about making mke2fs run e2image and saving the result
    > somewhere else, but that takes a long time, and people would get
    > annoyed if I did that. Still, enough people have gotten screwed by
    > this that I've been tempted to add this as an option. Another
    > possibility is for mke2fs to notice when the filesystem is already
    > formatted using ext2/3, and then printing a warning message and
    > waiting 10 seconds before continueing, so the user has a chance to
    > type control-C. This would probably be the least annoying as far as
    > already existing scripts that use mke2fs, although of course there
    > would be an option to turn this behaviour off.
    > > i did a cat /dev/hdaX > /dev/hdaY, which was an empty
    > > partition earlier so that I can play around a bit. I
    > > tried couple of things with debugfs but coudn't go
    > > much far.
    > You can use a disk editor to find the text strings of critical files
    > that you wish to rescue, and hope they were contiguously allocated,
    > but that's probably the best you can do....
    > Sorry, but that's the current Unix design philosophy, which is to
    > assume that the system administrator knows what he/she is doing. I
    > never, ever type the mke2fs command without a certain amount of fear
    > and trepidition, and always check and triple check before doing so.
    > Still, as Linux becomes more mainstream, we do need to think about
    > adding safety checks so that to avoid accidents by less careful system
    > administrators. The challenge is to figure out ways of doing so in
    > the least obstrusive way as possible, to avoid annoying the existing
    > population.
    > - Ted
    > P.S. The other approach, which might also be the right one, is to use
    > a front-end program --- call it newfs --- which does many more safety
    > checks and which could do things like use e2image to backup the inode
    > blocks before doing an mke2fs. That way, administrators can choose
    > whether they want the additional safety checks or not.
    > -
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